ELi5: When giant ships like the Titanic sink is there a whirlpool effect that can drag people under when the ship fills with water? Can someone please explain why or why not this would happen?
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To add to other answers a very similar effect can happen in air and it has pulled airplanes out of the sky. We don’t have man made things big enough to do this to airplanes, but water can do it. It’s called a microburst. Basically something causes a small stormcloud or part of a larger one to quickly and violently rain most of it’s water. This causes a massive downdraft as the water displaces and pulls air down with it. The air that goes down goes out and up and the air above and to the side is pulled in and down.
Let’s get this out of the way.
The effect is a real thing that happens with large ships.
The Mythbusters did one small scale test, with a boat far too small for the effect to be noticeable.
There are many accounts and engineering studies showing that the effect happens.
You need a large ship such as the battleship HMS Hood, and it needs to go down fast (the Hood went down in a few minutes after it blew up)
As to why it works.
Ever move you hand through a pool of water?
Behind you hand there’s less water because your hand pushed it away, so water fills in that place. The water moving into fill that place is what’s sucking you down.
If your hand moves fast, the water has to move fast to fill the space.
Also there’s air trapped in a large ship that bubbles up to the surface as the ship goes down. In some cases, the bubbles make the water light enough to make it impossible to swim or float. The air going up also displaces water, causing it to rush in from the sides.
It’s a real effect, but the actual magnitude will depend a lot on many factors (where you are relative to the ship, how big it is, how fast it’s sinking, shape, orientation, etc.).
Basically, a sinking ship is a big blunt object moving through the water. It happens to be moving down but that’s not particularly important. What is important is that, in order for the ship to move, water has to fill in behind it. This means that, on the backside of any object moving through water, there has to be some flow inwards and *towards* the center of the object to fill in the volume vacated by the moving ship. For a blunt shape, like a ball or a ship going straight down, you’re also going to have a recirculation zone behind it (check out this picture of a ball in a flow: [Solved: Figure 2: The Flow Around A Sphere On A Stick. Que… | Chegg.com](https://www.chegg.com/homework-help/questions-and-answers/figure-2-flow-around-sphere-stick-question-2-drag-sphere-25-fast-following-spheres-travel–q46536877) )
If you get into that current that’s rushing in towards the center or into the recirculation zone, there could be a very large drag force on you tending to pull you towards the ship.
When a ship goes down it leaves a giant column of air above it. Water then rushes in to fill in this column, dragging everything with it. The moving water is the fabled whirlpool effect.
This is also what causes tsunamis, but at a much larger scale. A plate drops (or rises), water is displaced and it forms a giant wave. Fortunately, ships can neither drop as fast as a tectonic plate, nor does it displace enough water, so sinking ships don’t cause tsunamis.
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